1. Field of the Invention
The present invention relates generally to a coil insertion device for inserting a stator coil into a slot defined within a stator core of an electric rotary machine. More specifically, the invention relates to an improvement of a mechanism for inserting a stator coil into a slot.
2. Description of the Related Art
Japanese Examined Patent Publication (Kokoku) 63-43988 discloses a coil insertion device which forms a background art of the present invention.
FIG. 1 shows the conventional coil insertion device. The device in FIG. 1 is illustrated in a position prior to inserting a coil. The shown construction will be discussed herebelow. In the exemplary construction, the device includes twelve blades 11 circumferentially arranged at predetermined intervals, for forming an annular body 13. The annular body 13 is fixed on a base plate 14 by means of an annular holder 15, and a stripper 16 is disposed within the interior of the annular body is for axial movement with respect thereto. Twelve projections 17 extend radially from the outer periphery of the stripper 16 for engagement with clearances in the annular body 13 defined by the intervals between the respective adjacent blades 11, and each of the projections 17 has a tapered shoulder 18 at the top end thereof. Wedge pushers 19 are formed integrally with the stripper 16 and extend radially from the lower end portion of the stripper. The stripper 16 is rigidly connected to a drive shaft 20 which is, in turn, connected to a hydraulic cylinder (not shown) for driving the stripper in the vertical direction. A stator core 21 is mounted on the blades 11, and defines a plurality of slots 22. A stator coil 23 is to be inserted into the respective corresponding slots 22 of the stator core 21, and wedges 24 are provided to be inserted into the slots 22 to thereby secure the associated stator coil 23.
The operation of the device set forth above will be discussed herebelow. When the stator coil 23 and the wedges 24 are to be inserted into the plurality of slots 22 in the stator core 21, by the thus-constructed coil insertion device, the wedges 24 are set on the wedge pushers 19, the stator coil 23 is hooked between the respective clearances between the adjacent blades 11, and the stator core 21 is engaged with the outer peripheries of the blades 11. FIG. 2 shows the positionin in which the coil is inserted by means of the conventional coil insertion device as set forth above. As seen from this figure, the drive shaft 20 is driven upward by the hydraulic cylinder, to thereby push the stripper 16 upward, and during this upward travel of the stripper 16, the tapered shoulders 18 of the projections 17 push the associated stator coil into the slots 22.
There are growing requirements for a higher quality insertion device with a smaller size, lighter weight, higher output, and so forth, but when an attempt is made to obtained higher density of coils in the stator core, by using of the conventional coil insertion device, the following problems may be encountered. FIG. 3(a) through 3(c) are side elevation views showing the process of the insertion of the coil by the conventional coil insertion device. As shown in FIG. 3(a), a plurality of the stator coils 23 are pushed toward the associated slots 22 by the tapered shoulders 18 of the stripper 16, and thus inserted into the slots 21, and by a further upward travel of the stripper 16, the respective stator coils 23 are forced to rotate into a vertical position to be set within the slot 22 of the stator core 21, as shown in FIG. 3(b). During this process, discrepancies such as a displacement can occur between the portions of the stator coils 23 directly pushed by the tapered shoulders 18 and the portions of the stator coils positioned away from the tapered shoulders, and as a result, the stator coils 23 can not be positioned precisely vertical, and thus are at an oblique angle with respect to the axis of the stator core 21, as shown in FIG. 3(c). Furthermore, as can be seen from FIGS. 3(b) and 3(c), the constituent conductors of the stator coils 23 set within the slots 22 are arranged at random. FIG. 4 shows a partial plan view of the stator core 23, in which the stator coils 23 are set in the slots 22. This figure shows the part of stator core 21 formed with a plurality of slots 22. The stator coils 23 are inserted into every two slots 22 by the projections 17 of the stripper 16 extending through the interval clearances 25 between the blades 11. As can be seen from FIG. 4, it was inevitable, in the conventional coil insertion device, that a relatively wide spaces to be occupied by the stator coils 23 be randomly arranged within the slots 22, and this hinders an increase of the density of the stator coils.
Furthermore, since the stator coils 23 and the wedges 24 are driven simultaneously with the common stripper, the dimensions can be fixed by a jig. This clearly limits the range of application of the axial length of the stators, for which the coil can be inserted with the common jig. Further, since all stator coils and all wedges are simultaneously driven, a substantial operating force, e.g. 2,000 kg to 4,000 kg, is required due to a high frictional resistance. Also, a tool is required for positioning the stator, but an adjustment of the position of the stator by the tool becomes difficult after the insertion of one or two layers. Therefore, there is a need for a way of adjusting the coils while avoiding interference by the tool.
Furthermore, as set forth above, the conventional coil insertion device inserts the stator coils 23, with a necessary number of conductors, simultaneously with the wedges 24. To obtain a higher quality, it is necessary to divide the required number of conductors of the stator coils into several units, to thereby insert these units one-by-one through a plurality of stages of the insertion operation, rather than inserting the necessary number of conductors at a one stage of the inserting operation. When this is performed by the conventional coil insertion device, the inserted coil unit can be forced out of the associated slot 22 by the wedge 24 simultaneously inserted with the coil.